118 replies to this topic

[dosco]

Interesting food for thought/discussion.....

It's my understanding that the octane rating is a measure of predetonation of the compressed fuel charge in the cylinder, just prior to ignition by spark plug. Now, I always hear (from various outlets) that one should use the octane rating as specified in the owner's manual. I am not one to believe that higher octane fuel leads to better gas mileage, but I do think that predetonation is a bad thing....

Back in 1993 I purchased a Saturn SL2.....4 cyl, 1.9L DOHC, FI, manual transmission, naturally aspirated, etc. The owner's manual specified 87 octane unleaded gasoline. When used, the 87 octane would predetonate (as evidenced by engine "pinging"), mostly at lower revs/higher engine loads. Engine compression ratio was something like 13.5:1, and the engine, fuel injection, emissions, etc., were all controlled by a main engine computer.

When I switched to 94 octane Shell pump fuel, the pinging was eliminated. Back then I was single and had "plenty of money," so I regularly used the more expensive 94 octane fuel (since I didn't like the pinging noises).

Isn't the main engine computer, in tandem with the intake and exhaust sensors, etc., supposed to automatically adjust the fuel/air ratio to prevent predetonation in 87 octane pump fuel?

Why would the automotive industry continue to recommend the use of fuel that predetonates regardless of the "control" provided by the main engine computer? (unless they *want* your car engine to self-destruct via predetonation, and force you into the purchase of another car)....

What kind of octane ratings do the F1 cars use with their "pump fuel?" 100 LL?

[Greg Locock]

Usually the calibration is set to suppress det. However, some manufacturers run full durability on their engines pinging continuously. Consequently those manufacturers can afford to run their engines in slight det whenever it suits them, to improve fuel economy and ,possibly, performance.

Incidentally the ignition advance curve is not always closed-loop - there may be speeds or throttle conditions where the knock sensor is no good, or they may have found that open loop is good enough, so they leave the knock sensor off.

[desmo]

As regards F1, I understand the octane rating is essentially irrelevent as detonation is simply not an issue at the rpm in the working range there.

[Wuzak]

The octane rating of fuel used in F1 is explicitly set out in the technical regulations.

I think it is 98-100 RON octane.


The amount of a number of the chemicals used in the fuel is also specified/limited.

[MRC]

Could you explain to me how detonation, slight or otherwise, will improve fuel economy and performance?

[Rainer Nyberg]

Article 19.3 in the current Tech Regulations for F1 states a minimum RON 95 and maximum 102 RON.
Max allowed MON number which is measured differently is 85.

[MaDDim]

Originally posted by dosco
Interesting food for thought/discussion.....

Back in 1993 I purchased a Saturn SL2.....4 cyl, 1.9L DOHC, FI, manual transmission, naturally aspirated, etc. The owner's manual specified 87 octane unleaded gasoline. When used, the 87 octane would predetonate (as evidenced by engine "pinging"), mostly at lower revs/higher engine loads. Engine compression ratio was something like 13.5:1, and the engine, fuel injection, emissions, etc., were all controlled by a main engine computer.

When I switched to 94 octane Shell pump fuel, the pinging was eliminated. Back then I was single and had "plenty of money," so I regularly used the more expensive 94 octane fuel (since I didn't like the pinging noises).

:

First of all your machine could not have 13,5:1 compression ratio. There isn't any car in production with more than 11:1 exept of course some exotic cars. If you had 13.5:1 then even a fuel with 98 octane wouldn't do the work. You would still have pinging and "cracks". In general the more compression you have the more octane your machine would demand for better performance and smoother running. :yawn:

[Greg Locock]

" Could you explain to me how detonation, slight or otherwise, will improve fuel economy and performance?"

Not really. I know the curve of spark for best torque is often compromised by the knock limit, and our calibration engineers call knocking 'the sound of economy'!

As I understand it there are two forms of knock, which sound very similar. One is pre-ignition, which octane rating has a big effect on, and is unaffected by the timing, the other is end-gas detonation, which is largely controlled by the mixture and swirl(?), and is affected by the timing as well.

[MRC]

Well, I imagine the torque output is knock limited. Typically an engine is tuned (for SA) for best torque (and the minimum SA required for that). In your typical SI engine, torque output is often knock limited. I would imagine that they are backing off the ignition advance some amount from the knocking point. Like Desmo also mentioned, a F1 engine (or any other very high revving engine) is not going to be knock limited. The torque will have a peak to it. Too much advance and the torque will start falling off.

Just FYI, but "pre-ignition" is not knock, it simply is just that the charge has been ignited before the spark was initiated. Pre-ignition can lead to knock, but they are not one in the same. You can pre-ignite by a few degrees, and the pressure trace (or sound) is not going to look like knock. If you have a lot more degrees of pre-ignition or you were already on the "edge" I can see you getting into knock, if that's what you were speaking of. Also, while many people confuse this, octane has little to no bearing on the resistance to pre-ignition. Methanol is a good example of this. High octane with a high tendency towards pre-ignition.

[red300zx99]

Just wondering, what exotic car runs a 11:1 compression ratio. The only car that comes to mind with such high compression numbers are honda's. Those crazy Japs, gotta love um

[Wuzak]

Originally posted by red300zx99
Just wondering, what exotic car runs a 11:1 compression ratio. The only car that comes to mind with such high compression numbers are honda's. Those crazy Japs, gotta love um

Ferrari 575 Maranello

No. of cylinders 65° V12

Bore & stroke 89x77 mm
3.46 x 2.95 in

Unit displacement 79 cc
29.2 cu. in.

Displacement 5,748 cc
350.7 cu. in.

Compression ratio 11:1

Maximum power 379 kW (515 bhp) at7,250 rpm

Maximum torque 588,6 Nm (60 kgm) at 5,250 rpm



There is just one.

[Bex37]

Originally posted by MRC
Could you explain to me how detonation, slight or otherwise, will improve fuel economy and performance?

Leaner fuel/air mixtures (better fuel economy) do tend to run a hotter combustion chamber temperature, which promotes pre-ignition. You don't necessarily have to have the motor pinging to be getting the best fuel economy out of it; under a lot of circumstances the fuel/air ratio can be run lean without risking pre-ignition.

[Bill Sherwood]

Originally posted by red300zx99
Just wondering, what exotic car runs a 11:1 compression ratio. The only car that comes to mind with such high compression numbers are honda's. Those crazy Japs, gotta love um

Toyota generation 4B 3SGE, as fitted to the Altezza.
11.5:1 compression
86mm x 86mm bore/stroke.
~200hp from two litres.
Titanium valves.
Fully variable inlet and exhaust cam timing.

[dosco]

Originally posted by MaDDim
:

First of all your machine could not have 13,5:1 compression ratio. There isn't any car in production with more than 11:1 exept of course some exotic cars. If you had 13.5:1 then even a fuel with 98 octane wouldn't do the work. You would still have pinging and "cracks". In general the more compression you have the more octane your machine would demand for better performance and smoother running. :yawn:

Yep, you're right.....9.5:1.

I was working from my (sometimes bad) memory. I traded the darn thing in a couple of years ago.

Served me well, though.

And yes, I did notice better "smoothness" when running 94 octane gasoline.

[dosco]

Originally posted by MRC
Also, while many people confuse this, octane has little to no bearing on the resistance to pre-ignition. Methanol is a good example of this. High octane with a high tendency towards pre-ignition.

Well, I thought I wasn't confused about it, but perhaps I am ;)

I always thought the confusion lied in the misconception that "octane" was some type of hydrocarbon added to the gasoline to "improve performance." Then, in my travels, I once read that the octane rating really was a system devised to categorize a fuel's resistance to predetonation.

Please explain the octane rating system.

[JwS]

Octane is a hydrocarbon, it was chosen as the standard, pure Octane is rated "100". Fuels are judged by putting them in a variable compression 'test engine' and increasing compression to the detonation point. This is compared to Octane as a fuel in the same setup to get the rating.
Don't ask me why Octane was choosen, I have never heard a reason.
I don't know what the configuration of the 'test engine' is, it is some kind of single cylinder lab thing, it may or may not be spark ignition, I guess it wouldn't need to be?? anyone know more?
JwS

[dosco]

Just got this on "howstuffworks.com"

"The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.

It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.

During WWI, it was discovered that you can add a chemical called tetraethyl lead to gasoline and significantly improve its octane rating. Cheaper grades of gasoline could be made usable by adding this chemical. This led to the widespread use of "ethyl" or "leaded" gasoline."

Cool.....

[dosco]

Originally posted by JwS
Octane is a hydrocarbon, it was chosen as the standard, pure Octane is rated "100".

Makes sense, but then how do you get "115 Octane" (aviation fuel)?

[VAR1016]

Originally posted by dosco


Makes sense, but then how do you get "115 Octane" (aviation fuel)?

You have to let go of the idea that octane actually needs to be present (even if it usually is).

For example, pure methanol has a RON of 118 and a MON of 112. Remember that the octane rating of a fuel is a relative term: related to the performance of pure octane as described above. When thus related, various substances have ratings greater than 100. And of course you could add tetra-ethyl lead to pure octane and enjoy a rating greater than 100 (plus the "lead bonus" that gives a higher MON). It is worth noting that American road fuels sensibly are defined by adding their RON and MON together and dividing the result by 2; thus American 94-octane fuel is probably equivalent to a British 100-octane one.

Benzene and Toluene from the aromatic group of hydrocarbons (equal number of carbon and hydrogen atoms in the molecule) have octane ratings higher than 100. Benzole derived from coal tar, is another. There are more modern additives such as MTBE (Methyl-tertiary-butyl-ether) that are used in modern road fuels.

It is interesting to note that in France it is possible to buy a gasoline that would be illegal in F1: you can find fuel with a MON of 88; my Fulvia loves it!

PdeRL

[dosco]

Originally posted by VAR1016


You have to let go of the idea that octane actually needs to be present (even if it usually is).

For example, pure methanol has a RON of 118 and a MON of 112. Remember that the octane rating of a fuel is a relative term: related to the performance of pure octane as described above.

I was making a bit of a tongue-in-cheek comment....trying to be a bit lighthearted, you know ;)

Anyway, I'm not suprised by your statement, since the whole affair is arbitrarily based on the fact that octane is resistant to predetonation. I'm sure that there are all kinds of aromatic hydrocarbons that are extremely resistant to predetonation, so much so that the "octane ratings" could potentially be "off scale high."

It's also my understanding that the octane rating of most (or all) US pump fuel is adjusted by the addition of MTBE to prevent predetonation, and that the actual rating itself is more of a measure of resistance to predetonation than anything else.

(also explains the addition of benzene and toluene to the "F1 witch's brew" of the early 1990s)

Interesting to discuss, though....you learn something new every day

[VAR1016]

Originally posted by dosco


I was making a bit of a tongue-in-cheek comment....trying to be a bit lighthearted, you know ;)

Anyway, I'm not suprised by your statement, since the whole affair is arbitrarily based on the fact that octane is resistant to predetonation. I'm sure that there are all kinds of aromatic hydrocarbons that are extremely resistant to predetonation, so much so that the "octane ratings" could potentially be "off scale high."

It's also my understanding that the octane rating of most (or all) US pump fuel is adjusted by the addition of MTBE to prevent predetonation, and that the actual rating itself is more of a measure of resistance to predetonation than anything else.

(also explains the addition of benzene and toluene to the "F1 witch's brew" of the early 1990s)

Interesting to discuss, though....you learn something new every day

Oh sorry! I missed that

However I have always thought that fuels are a very fascinating subject.

In fact I was puzzled years back; I had assumed that since the early 1960s "pump fuel" was supposed to be used in F1 cars. And then we heard rumours in the 1990s in the 3.5 litre era that teams were using super fuels alleged to give a bonus of as much as 50 horsepower.

Of course these were banned, but I would like to know if or when they were permitted - was it for the turbo era perhaps?

I was told of a synthetic hydrocarbon called CUBANE. I understood that its molecule was cuboid, hence the name. I have a feeling that its chemical formula was C8H8. Apparently it was produced in a laboratory at stupendous cost - something like £100 per litre!

PdeRL

[dosco]

Originally posted by VAR1016


Oh sorry! I missed that

Of course these were banned, but I would like to know if or when they were permitted - was it for the turbo era perhaps?

I was told of a synthetic hydrocarbon called CUBANE. I understood that its molecule was cuboid, hence the name I have a feeling that its chemical formula was C8H8. Apparently it was produced in a laboratory at stupendous cost - something like £100 per litre!

Don't worry about missing the humor. For all you know I don't know diddly.....

I'm not sure there was ever a rule allowing the "super fuels," but I distinctly recall seeing pics of guys in HAZMAT suits fiddling with drums of elf fuel prior to the start of an F1 race. This was back in '92 when I was getting into the sport....I don't have the mag - it was my buddy's - but the caption said something like:

"today's F1 cars run on a witch's brew of Benzene, Toluene, and other hazardous chemicals that deliver up to an additional 50 hp for peak performance"

Looked pretty scary to me.....imagine "enjoying" the smell of race fuel and then finding out it's combusted "dry cleaning chemical!!

CUBANE huh? Any URLs or other data? Sounds interesting.....and toxic!

[VAR1016]

Well, the best known aromatics are Benzene, Toluene and Xylene - in ascending order of volatility. Xylene is, or at least was, a central constituent of car paints. They all have excellent octane properties and all (like virtually everything it seems) are carcinogenic. For reasons that are not clear to me, aircraft fuels apparently have to be high octane; perhaps in anticipation of thin air with the risk of lean mixtures leading to detonation.

Avgas is usually coloured blue.

Years ago I was with a friend (actually at that time my employer - he had a garage specialising in Porsches; we had a Superflow dynomometer which was great fun) who was racing a Porsche at Donnigton Park. He had a knack of changing engines very quickly and used to enter in two races quite often. This time he was using a turbo-charged engine that was fitted with the (in my view) inept Bosch K-Jetronic injection. Anyway I think that he had fiddled with this and the car was not going properly - in fact he had been round quicker with his 2.2-litre engine fitted. I suspected that it was either lean, or the fuel was not up to the job. At that point, a customer of my friend who was also in the race appeared with a devilish grin on his face asking what was happening. We explained and he said "Would you like to try some of my petrol?" He brought over a jerry-can and out the stuff poured. God knows where he got it from!

The cubane story came from a customer at another garage; he was a technical librarian specialisig in chemistry; I have no idea where he found the information.

However I am willing to bet that someone hereabouts knows the story!

PdeRL

[VAR1016]

Whoops! Mistake - thin air of course mean rich mixture.

Perhaps aircraft run high compression ratios although I doubt it. I suppose it could just be a fail safe of some sort.

I wish I had a friend at an aerodrome!

PdeRL

[VAR1016]

Sorry again; the first of my last two posts became corrupted.

The "petrol" that was donated to us was blue and smelt like paint thinners.

My pal did a couple of laps and came back with a big smile on his face!

PdeRL

[Wuzak]

I thought that it was the early '80s, in the Turbo era, when all the really toxic rocket fuels were being used.

I read that BMW engineers found a fuel mix that was originally used by the Luftwaffe in WW2.

[dosco]

Originally posted by VAR1016
Whoops! Mistake - thin air of course mean rich mixture.

Perhaps aircraft run high compression ratios although I doubt it. I suppose it could just be a fail safe of some sort.

I wish I had a friend at an aerodrome!

PdeRL

IIRC they run fairly high compression ratios. I'll crack open my old schoolbooks and check.......

As far as lean/rich....that is controlled by the engine's main computer, and the configuration of the combustor. The key is to have a "rich" central burning zone with the stochiometric fuel/air ratio correct for a particular altitude. and a "lean" outer burning zone that acts as an insulating barrier between the *very* hot central zone and the metal of the combustor. Of course, adding to the insulation are the "dilution holes" in the combustor that provide a thin film of "cool" uncombusted air thus keeping the metal of the combustor below its melting point....

[dosco]

I think I already know the answer to this one......what about Nitromethane?

[desmo]

A google search on cubane provided an interesting diversion. First synthesized by a University of Chicago chemist in 1964, cubane has a unique cubic molecular structure hor a hydrocarbon with its bond angles at 90 deg (as you'd expect from the name) creating a LOT of strain energy as hydrocarbons like to bond at closer to 120 deg. It appears to be a stable solid at standard T and Ps, so I guess it isn't likely to be a fuel additive if it isn't highly soluble in one of the other fuel constituants. It is also hugely expensive apparently, though I did find a commercial source for it.

An NO2 group at each corner creates octanitrocubane, which shows considerable potential as a very powerful yet stable explosive or solid rocket propellant. Cool.

[MaDDim]

It was rumored that the best 3.5L F1 engines in the beginning of the 90s before the banning of "exotic" fuels where about 800-850hp. I don't know if that is true but it was also heard of usinng fuels with almost 130 octane rating. Pretty amazing isn't it?They also had an awful smell...

[dosco]

Originally posted by VAR1016
Whoops! Mistake - thin air of course mean rich mixture.

Perhaps aircraft run high compression ratios although I doubt it. I suppose it could just be a fail safe of some sort.

I wish I had a friend at an aerodrome!

PdeRL

OK, checked a couple of sources......

"Jet and Turbine Aero Engines" by Bill Gunston.....Bill discusses how "today's compressors" have a pressure ratio (same as compression ratio) of 40:1.

Went to the CFM-56 website (the CFM-56 is the "standard" engine for the Boeing B737.....CFM is a joint venture between GE and SNECMA)....the CFM-56-7 pressure ratio is 32:1.

Pretty high compression, no? The difference, though, is that the air is compressed first, then the fuel is added. I don't think predetonation is much of an issue.

On an interesting side note, when I was in the USAF, there were manuals describing the use of different fuels for the jet aircraft. Straight gasoline (preferably 100LL) could be used, but since it burns so hot, the engine would have to be removed/inspected/rebuilt after use.....consequently the use of gasoline as a jet aircraft fuel was strictly for emergency use only.

Jet fuel is a blend of gasoline and kerosene.....

[Wuzak]

I wouldn't think that detonation of any kind is possible in a turbine engine.

The fuel is burned continuously, and is introduced into the already compressed air.


It would be an issue in piston engined aircraft though. These tend to be lower revving.

[dosco]

Originally posted by Wuzak
I wouldn't think that detonation of any kind is possible in a turbine engine.

The fuel is burned continuously, and is introduced into the already compressed air.


It would be an issue in piston engined aircraft though. These tend to be lower revving.

Yes, as you stated the fuel is added after the air is compressed, so a turbine engine cannot predetonate in the same fashion as a piston engine (where the fuel is added *then* the fuel/air mixture is compressed).

Yes, it would be a problem on a piston-engine aircraft.....since the operating cycle of the piston engine in the airplane is the same as that of an automobile.



Now, in a turbine engine there is a "detonation" of a sort when there is a "compressor stall." Sounds like a bomb going off!

[Wuzak]

Originally posted by dosco



Now, in a turbine engine there is a "detonation" of a sort when there is a "compressor stall." Sounds like a bomb going off!

Which is, of course, another completely different phenomenon!

I have never heard that myself. Does it actually do damage to the turbine blades?

[dosco]

Originally posted by Wuzak



Which is, of course, another completely different phenomenon!

I have never heard that myself. Does it actually do damage to the turbine blades?

Yes, compressor stall has nothing to do with "predetonation."

It happens when the airflow around the compressor blades stalls (the very same as when an aircraft wing has a stall). It is caused by inlet flow distortions (like sucking in a vortex during a high angle-of-attack maneuver) and engine case flexure.

Depending how bad the compressor stall is, yes, it can cause damage.....these days you don't see much in the way of compressor stalls due to the use of computer controlled variable stator vanes (VSVs) which "protect" the compressor from inlet flow distortions. Also the blades are high-end metallurgical products, so they're quite robust. But I have heard of damage induced by compressor stalls....

[VAR1016]

Originally posted by dosco


Yes, as you stated the fuel is added after the air is compressed, so a turbine engine cannot predetonate in the same fashion as a piston engine (where the fuel is added *then* the fuel/air mixture is compressed).

Yes, it would be a problem on a piston-engine aircraft.....since the operating cycle of the piston engine in the airplane is the same as that of an automobile.



Now, in a turbine engine there is a "detonation" of a sort when there is a "compressor stall." Sounds like a bomb going off!

Yes of course I was referring to piston-engines.

Interestingly there is ana ccount of this "bomb" effect in the new BRM book by Doug Nye and Tony Rudd. This concerns the Rover-BRM gas turbine Le Mans car that ran at La Sarthe in 1963 and 65. The "bomb" gave Graham Hill quite a start!!

PdeRL

[ray b]

is the % of MBTE, the modern anti-knock stuff the only real difference in hi-test pump gas??
or is the regular gas realy cheaper to make or are we getting ripped off by the over priced HI-test
how much does it cost to add the MBTE to HI-test

is regular gas more powerfull in BTU's and hi-test just less exploseve because of the added MBTE??

will a normal compression motor gain or loose power if over octained, if not computer controled to advance spark timing

[VAR1016]

Originally posted by ray b
is the % of MBTE, the modern anti-knock stuff the only real difference in hi-test pump gas??
or is the regular gas realy cheaper to make or are we getting ripped off by the over priced HI-test
how much does it cost to add the MBTE to HI-test

is regular gas more powerfull in BTU's and hi-test just less exploseve because of the added MBTE??

will a normal compression motor gain or loose power if over octained, if not computer controled to advance spark timing

This raises an interesting point: methanol with its very high octane value is actually a poor fuel compared with gasoline. Gasoline has a very high specific heat value, so to get the same amount of energy, one has to burn (I think) four times as much methanol.

There was another thread explaining why there is a minimum octane value for F1; this is because the engines run so fast, that a quicker-burning fuel is very useful.

PdeRL

[JwS]

There are all sorts of funky things that can be done with fuel and still fit ‘the rules’. I can pay upwards of $15+ a gallon for fuel for my race bike that meets the specific gravity requirements, but will boost hp by 5% or so. It is ‘oxygenated’ so it supplies some oxygen when burned, you have to richen the mixture to use it to full advantage. But it smells really toxic. The regular stuff, which is a more conventional brew, but fast burning for motorcycles, has a really great smell, especially the exhaust, or maybe it is just me. (and something like 111 octane, but the fuel guy says that measured octane isn't really the whole story.....)
JwS

[MRC]

VAR1019, you have to calculate the amount of energy release for a maximum output mixture. So, to say another way, you can compare the energy output of methanol for a stoich mixture and a gas mixture at stoich. Obviously you need to dump in a larger weight/volume of methanol. But to really know how much power you can make, you need to compare each fuel at their representative max power mixtures. So gas might be .88-.90 lambda, but methanol might be .82-.88 lambda. Depends somewhat on setup.

But methanol also has a higher specific heat, so it can cool the intake charge, and you can get even more fuel in. Even without rasing compression ratio, or boost, or whatever, you can get a power increase from methanol from this effect alone. So methanol is actually a pretty nice fuel, besides it having no visible flame, and being poisonous, and caustic.

[VAR1016]

Originally posted by MRC
VAR1019, you have to calculate the amount of energy release for a maximum output mixture. So, to say another way, you can compare the energy output of methanol for a stoich mixture and a gas mixture at stoich. Obviously you need to dump in a larger weight/volume of methanol. But to really know how much power you can make, you need to compare each fuel at their representative max power mixtures. So gas might be .88-.90 lambda, but methanol might be .82-.88 lambda. Depends somewhat on setup.

But methanol also has a higher specific heat, so it can cool the intake charge, and you can get even more fuel in. Even without rasing compression ratio, or boost, or whatever, you can get a power increase from methanol from this effect alone. So methanol is actually a pretty nice fuel, besides it having no visible flame, and being poisonous, and caustic.

Oh yes, I had not intended to criticise methanol's worth as a fuel - as you rightly point out, its cooling properties are one of its key advantages, plus of course before electronics, enormous boost pressures and/or compression ratios could be used fairly safely. The Alfa-Romeo 158/9 springs to mind, where much of the fuel was passed straight through just to keep the engine's insides cool. Its fuel consumption was 1.5 mpg; even the V16 BRM could manage about 3mpg!

Ferrari realised the fuel consumption problem, so his 2-litre cars ran on a 50/50 petrol/methanol mix and apparently, he got the amazing figure of 12mpg, which is about what I get from my 1600cc Lancia on a track day.

Certainly I could live without methanol's physical properties. Still, there's always ethanol which is nearly as good and has other applications too (!)

Meanwhile as you are obviously very knowledgable, could you tell me why acetone was often added to racing fuels? I know that before the war, Mercedes-Benz and Auto-Union certainly used fuels containing acetone.

Thanks

PdeRL

[MRC]

I believe it's usually added (at least in conjunction with methanol as the main ingriedient) to add in starting and to reduce tendency towards pre-igntion. Do a search on fuel or octane FAQ. There is one on the internet, that is quite good.

[VAR1016]

Originally posted by MRC
I believe it's usually added (at least in conjunction with methanol as the main ingriedient) to add in starting and to reduce tendency towards pre-igntion. Do a search on fuel or octane FAQ. There is one on the internet, that is quite good.

Thanks very much - Iwill.

If it resists pre-ignition, then I expect it must have good octane qualities itself; and I know where there's a little drum of the stuff too!!

PdeRL

[VAR1016]

Originally posted by MRC
I believe it's usually added (at least in conjunction with methanol as the main ingriedient) to add in starting and to reduce tendency towards pre-igntion. Do a search on fuel or octane FAQ. There is one on the internet, that is quite good.

I had a search around and found some interesting and quite diverting stuff.

Yes, Methanol and Acetone can be used to inhibit pre-ignition.

10% acetone added to gasoline will yield a 3-point octane improvement.

10% methanol yields 5 points - and by the way I was wrong: methanol's RON is apparently 133.

Acetone is however more economical in terms of consumption than methanol.

I found this site: http://www.turbofast...u/racefuel.html

PdeRL

[H. Eckener]

Gasoline FAQ

Kettering assigned Thomas Midgley, Jr. to the task of finding the exact cause of knock [24]. They used a Dobbie-McInnes manograph to demonstrate
that the knock did not arise from preignition, as was commonly supposed, but
arose from a violent pressure rise *after* ignition. The manograph was not
suitable for further research, so Midgley and Boyd developed a high-speed
camera to see what was happening. They also developed a "bouncing pin"
indicator that measured the amount of knock [9]. Ricardo had developed an
alternative concept of HUCF ( Highest Useful Compression Ratio ) using a
variable-compression engine. His numbers were not absolute, as there were
many variables, such as ignition timing, cleanliness, spark plug position,
engine temperature. etc.

[H. Eckener]

Purely a general trend of lean mixtures.

[MRC]

Here was the gasoline FAQ I was talking about.

http://www.faqs.org/...line-faq/part1/

[MRC]

Oh, it's the same one as H.Eckener posted, just on a different site. There are four parts to it though. Read them all.

[HJK]

According to f1-live.com , Shell is producing a light wieght fuel. It supposedly will give a car an extra 20% distance over the same weight of traditional fuel.
Is this possible? How might it be done?

[masterhit]

Using a compound that is just as efficient with a smaller density of molecular structure?